Central Nervous System
Brain and spinal cord
Protected by:
The skull and vertebral column
Bony armor
The meninges
A triple layer of connective tissue
Cerebrospinal fluid between
the meninges aids in cushioning
The blood-brain barrier
Relatively impermeable brain
capillaries
Keeps out microbes and
damaging chemicals
The Spinal Cord
Cable of axons protected by the backbone
Transmits signals between the brain and body
Grey matter
Cell bodies of motor and association neurons
White matter
Surrounds the grey matter
Myelinated axons
Send impulses up and
down the spinal cord
The Spinal Cord
Neural pathways for some simple behaviors (reflexes)
The Vertebrate Brain
Major anatomical and functional divisions
Hindbrain
Midbrain
Forebrain
These parts develop different sizes in different species
The Hindbrain
Medulla controls several autonomic functions, such as
breathing, heart rate, and blood pressure
The pons plays a role in the transition from sleep to
wakefulness, and regulates breathing rate
Cerebellum helps coordinate movements of the body
The Midbrain
The reticular formation
An important relay and sensory filtering station
Extends from medulla into lower regions of the forebrain
The Forebrain
Thalamus
Limbic system
Cerebral cortex
The Thalamus
Channels sensory information from all parts of the body
to the limbic system and cerebral cortex
The Limbic System
Produce our most basic and primitive emotions, drives,
and behaviors
The hypothalamus is a coordinating center between the
nervous and endocrine systems
The amygdala produces
sensations of pleasure,
fear, or sexual arousal
The hippocampus is
involved in emotional
behaviors and the
formation of long-term
memory
The Cerebral Cortex
Convoluted outer layer of the forebrain
Two hemispheres connected by a large band of axons
(the corpus callosum)
The Cerebral Cortex
Each hemisphere is divided into four
anatomical regions
Frontal lobe- motor,
intellectual functions
Parietal lobe- sensory
functions
Occipital lobe- vision
Temporal lobememory, language
comprehension,
hearing
The Cerebral Cortex
Each hemisphere is made of different functional areas
Primary sensory areas:
sensory signals
received, impressions
are formed
Association areas:
interpret sounds and link
stimuli with memories
Primary motor areas: in
the frontal lobe;
stimulate motor neurons
Living things respond to stimuli
What senses are these animals using?
The Brain interacts with the
outside world through senses
Sensory receptors transduce the energy of a specific
signal into an electrical signal - receptor potential
If the receptor potential is positive enough, an action
potential forms
The more positive the receptor potential, the higher the
frequency of action potential formation
Sensory Receptors
Mechanoreceptors
Sense mechanical stimulus- motion, touch, vibration
Mechanoreceptors- skin
Produce receptor potential when membrane is
stretched or dented
Free nerve endings
produce sensations
of itching, tickling,
and touch
Nerve endings
enclosed in
connective tissue
detect pressure
Other mechanoreceptors
In hollow organs signal fullness by responding to stretch
In joints to sense position of limbs
In inner ear to detect gravity,
motion, vibration (sound)
Fish mechanoreception
The lateral line
A row of hair cells along the body
Senses vibration and water movement
Mechanoreception & Sound
Sound waves are vibrations in fluid (air, water)
Mechanoreception & Sound
Outer ear captures sound waves and aids in sound
source localization
External ear: collects and directs sound waves
Auditory canal: carries sound waves to the middle ear
Mechanoreception & Sound
Middle ear transmits sound waves to the inner ear
Tympanic membrane: the
eardrum
Middle ear bones: transmit
sound vibrations to inner ear
Auditory tube: equalizes air
pressure between the middle
ear and atmosphere
Mechanoreception & Sound
Inner ear converts vibrations into electrical signals
Middle ear bones transfer sound energy into the
cochlea
Vestibular system: involved in balance
The Cochlea
Vibrations produce fluid movement tranmitted to the
basilar membrane
Basilar membrane vibrations cause hair cells to bend
against the tectorial membrane
Receptor potentials are formed, and action potentials
are sent to the brain
Sound Perception
Volume
Larger sound vibrations bend hair cells more
Very loud or prolonged sounds can damage hair cells
Pitch
Different parts of the basilar membrane vibrate at
different frequencies
Photoreception
All forms of vision use photoreceptors
Cells that contain photopigments that absorb light,
which produces chemical changes
When photopigments change, receptor potentials form
Eyespots
Basic light/dark reception
Not image forming
Compound Eyes
Arthropods
Many individual light-sensitive subunits - ommatidia
Each ommatidium forms a small part of a larger image
Pieced together to form a grainy visual mosaic
The Mammalian Eye
Collects, focuses, and transduces light waves
Cornea: transparent covering
Aqueous humor: watery fluid; nourishes lens and cornea
Sclera: white outer layer; tough connective tissue
Iris: pigmented ring of muscle; controls light entry
Pupil: opening in the center of the iris
The Mammalian Eye
Lens: transparent protein structure bends light- focus
Vitreous humor: jelly-like fluid; maintains eye shape
Retina: multilayered sheet of photoreceptors
Choroid: dark middle layer absorbs stray light; blood supply
helps nourish retina
The Adjustable Lens
Muscles attached to lens contract to change the shape
Fovea of retina - visual image is focused most sharply
Lens allows images to be focused on the fovea when
looking at objects at different distances
Common vision problems
Abnormally long eyeball:
the image is focused in front of the retina
nearsightedness
Abnormally short eyeball:
the image is focused behind the retina
farsightedness
Retinal Photoreceptors
Cones- color vision
Concentrated in the fovea
Require relatively bright light to function
Detect red, green, and blue light wavelengths
Rods- vision in dim light
Concentrated in the periphery of the eyeball
Perceive light intensities (shades of grey)
Transmitting the signal
Signal-processing neurons
Process receptor potentials and pass forward impulses
Ganglion cells
At the front of the retina
Carry action potentials to brain along optic nerve
The blind spot is where the optic nerve connects to eyeball
No photoreceptors, so images disappear
Eye placement affects vision
Carnivores and omnivores have forward-facing eyes
Eyes have overlapping visual fields
Allows depth perception (binocular vision), which
allows more accurate prey capture
Many herbivores have widely spaced eyes
Little visual field overlap
Near 360-degree field of view
Allows for easier predator detection
Chemoreception
Chemoreceptors detect presence of chemicals in fluids
Smell: detecting airborne or waterborne molecules
Taste: detecting molecules dissolved in water or saliva
Olfactory Receptors
Located in the upper nasal cavity
Hair-like dendrites protrude into a mucus layer
Odorous molecules in air dissolve in nasal cavity
mucus and bind to receptors on olfactory dendrites
Taste Receptors
Contained on tastebuds-about 10,000 on the tongue
Each taste bud contains 60-80 taste receptor cells
Taste receptor microvilli project out a taste pore
Dissolved chemicals enter the pore and bind to
receptors on microvilli
Taste Receptors
Allow the perception of flavors
sweet, sour, salty, bitter, and umami
Taste receptors are evenly distributed
Flavor combines with odor to produce taste
Pain
Perception of tissue damage
Pain receptors respond to two chemical stimuli
Potassium ions
Bradykinin is formed from
enzymes released from
damaged tissue
Some senses are unfamiliar to
humans
Echolocation
Use of sonar to hunt in darkness or murky waters
Bats have large ears and modified middle ear bones
Porpoises make ultrasonic clicks that are directed
through large, oil-filled sacs
Electroreception
Used to capture prey
Electric fish produce high-frequency electric fields
This field is perceived by electroreceptor cells
Objects near the field distort it, alerting the fish
Sharks use electroreception
Ampullae of Lorenzini concentrated on snout
Can detect prey from weak bioelectric signal
Electroreception
Also used in communication
Some electric fish can detect and recognize the signals of
potential mates
Magnetic fields
Some animals, such as birds and fish, can use the
Earth’s magnetic field to navigate over long distances
for migration
The Nervous System relies on
electric communication
The Endocrine System relies
on chemical communication
Chemical Communication
Direct communication from the inside of one cell to
the next occurs through gap junctions
Cells release “messenger molecules” that stimulate
cells if the molecules bind to receptor proteins
Like neurotransmitters in the nervous system!
Chemical communication
Paracrine communication occurs between nearby
cells using local hormones that diffuse through
extracellular fluid
Endocrine communication occurs between distant
cells using hormones that are carried by the
bloodstream
Paracrine communication
Local hormones produced by most cells
Example: prostaglandins
Are modified fatty acids used for local communication
Umbilical cord arterial constriction
Stimulate uterine contraction
Contribute to inflammation
Stimulate pain receptors
Endocrine Communication
Hormones released in response to stimuli
Glands make up the endocrine system
Travel through the circulatory system to reach target cells
Three Classes of Endocrine
Hormones
Amino acid-based hormones: synthesized from
single amino acids
Peptide hormones: made from chains of amino acids
Steroid hormones: made from cholesterol
Endocrine Hormones are Targeted
A cell will only be affected if it has receptors specific to
that hormone
Different classes of
hormones bind to receptors
in different ways
Differences in chemical
composition affect ability to
penetrate cell membrane
Hormone Solubility
Water-soluble
Most peptide and amino-acid based hormones
Cannot penetrate cell membrane
Water-soluble hormones use cell membrane receptors
Activates formation of a “second messenger” that
produces cellular effects
Lipid-soluble
Steroid hormones
Can easily penetrate cell membrane
Enter cell and bind to receptors in cytoplasm or nucleus
Resulting hormone-receptor complex activates genes
Regulation of Hormone Release
Most hormones are controlled by negative feedback,
which inhibits further release
In a few cases, positive feedback is used to amplify
hormone release
Mammalian Endocrine System
There are many animal hormones
The major functions of vertebrate hormones are well
established
(Summarized in Table 37-3, p. 747)
Exocrine and Endocrine Glands
Exocrine glands: produce secretions that are released
through a duct
Outside the body, or into body tubes and cavities
Endocrine glands: ductless and secrete their
hormones within the body
Released into interstitial spaces, enter capillaries, and
are transported through the circulatory system
The Hypothalamus and Pituitary
Coordinate many key hormonal messaging systems
Hypothalamus controls the pituitary gland
The Hypothalamus
Clusters of neurosecretary cells
Synthesize and store peptide hormones
Release when
stimulated
The Pituitary
Dangles below hypothalamus
Controls hormone release
Anterior pituitary
True gland
Posterior pituitary
Extension of
hypothalamus
Control of the Anterior
Pituitary
Hypothalamus hormones regulate release of
pituitary hormones
Releasing hormones
Inhibiting hormones
Anterior Pituitary
Hormones
Regulation of hormone production in other glands:
Gonads- production of sperm, eggs, and sex hormones
Follicle-stimulating hormone
Luteinizing hormone
Thyroid
Thyroid-stimulating hormone –release of thyroid hormones
Adrenal glands
Adrenocorticotropic hormone- release of cortisol
Anterior Pituitary
Hormones
Prolactin- development of mammary glands
Melanocyte-stimulating hormone- synthesis of
melanin
Growth hormone- regulates body’s growth
Control of the Posterior
Pituitary
Hormones produced in the hypothalamus
Cell bodies in hypothalamus
Neurosecretary cell endings in posterior pituitary
Posterior Pituitary
Hormones
Antidiuretic hormone- prevents dehydration
Oxytocin- contraction of uterus, milk letdown
reflex, pair-bonding in mammals
Thyroid
Base of neck
Metabolism- Thyroxine
Calcium levels- Calcitonin
Thyroxine
Elevates metabolic rate
Can also help regulate growth
Thyroid Enlargement
Low Iodine conditions
Thyroid attempts to compensate by increasing
number of thyroxine-producing cells
Enlarged thyroid is a goiter
Parathyroid
Embedded in thyroid gland
Secrete parathyroid hormone
Control concentration of blood calcium
Low blood calcium leads to release of PTH and
release of calcium from bone “storehouse”
Pancreas
Behaves as exocrine gland
Digestive secretions
And endocrine gland
Regulate blood glucose level
Insulin
Glucagon
Blood Glucose Regulation
Insulin reduces blood glucose level
Glucagon increases blood glucose
level
Gonads
Steroid hormones
Stimulated by LH and FSH from anterior pituitary
Increased during puberty
Testes- androgens, including testosterone
Ovaries- estrogen & progesterone
Adrenal glands
Located on the kidney
Two parts
Adrenal medulla
Adrenal cortex
Adrenal medulla
Located in center of adrenal gland
Produces epinephrine (adrenaline
And norepinephrine (noradrenaline)
Prepare body for emergency action (fight or flight)
Adrenal Cortex
Outer layer of adrenal gland
Secretes Glucocorticoids, including cortisol
Helps cope with short-term stressors
Raising blood glucose
Promoting fat breakdown for energy
Inhibiting immune system
Adrenal Cortex
Also secretes aldosterone
Regulates blood sodium content
Some testosterone
Minor compared to testes
Other hormone producers
Pineal Gland
Melatonin
Influences daily and seasonal rhythms
Thymus
Thymosin
Development of white blood cells
Other hormone producers
Kidneys
Hormones that influence blood production and volume
Heart
Hormone influences activity of the kidneys
Digestive tract
Many hormones that regulate digestion
Other hormone producers
Fat cells
Leptin
Tells body how much fat is stored and decreases
apetite
Link between obesity and leptin sensitivity